A book by Russ Lyman, Joe Ordonez, Mike Speaks - "The complete guide to the Tatshenshini River Including the Upper Alsek River". Is a good start. Lots of information - some a little dated maybe but a good place to start. It covers pretty much everything including permits, logistics and detailed description of the river.
The whitewater in the Canyon is for real. Narrow and fast with real holes, tight corners and walls. Not overly difficult but you will be pretty remote. Solid class III going to IV at higher levels. Most of river is just big, fast and cold. Wonderful trip. Alsek lake is amazing.
Good place to start. Shadow Lake Expeditions: raft rentals&wilderness trips in the Yukon
phone (867) 393-2232). Or Alaska River Outfitters | Haines Alaska
(phone 907 766 3307)
Too many options to list here but these folks should be able to help. When we did it we were self contained except shuttle driver between Dalton Post and Haines. We took 12 days - included 3 layovers. We used Yakutat Air out of Yakutat at Dry Bay. Worked well but not cheap. Good Luck.